The applicant is well skilled in the knowledge of hydraulic fluid flow control equipment. The unit as illustrated herein includes various components that are well known in the prior art. Such components include spool valves, relief valves, metering orifices and the like. After reviewing the appropriate prior art, it is the applicant's considered opinion that the art does not include a variable orifice arrangement which allows for the programming of differential pressures occurring between the inlet of the unit and the control chambers which allow ultimate delivery of fluid to the motors to be driven versus the flow volume to the motors. This can in no manner be accomplished through the use of a fixed orifice unit.
A fixed orifice unit will result in low pressure differentials at low flow and therefore limited control for the driving or driven motors and will result in high pressure differentials at high flow volume which provides precise control. It is at these lower flow volumes and low pressure differentials that control becomes essential. An example of required control is a two wheeled vehicle with one wheel positioned in sand or low traction medium with the other wheel being on a high traction medium. With the applicant's unit, a variable orifice flow control is provided and this orifice is programmable to greater differential pressures versus flow differentials at low flow and therefore control at low flow, and, similarly lower pressure diffentials at high flow resulting in less control and less pressure loss at higher vehicle speeds.
The variable orifice structure of the applicant's device is actually a sliding poppet or low pressure relief valve. The particular poppet design determines and changes the differential pressure changes versus the flow volume changes. Differential pressure variations between the two wheel or motor circuits result in control spool shift and resulting control and this design allows a greater acceptable flow increase from a "beginning control" flow.
In accordance with the background of the invention, it is therefore an object of the applicant's invention to provide a flow divider or combining device including control spools for the ultimate delivery of or receipt of hydraulic fluid to and from independent motors which are joined by an external force.
It is a further object of the applicant's invention to provide a flow divider or combining device which includes a variable orifice structure for the control of fluid flowing through the unit to at least two independent motors such control being in response to pressure losses and pressure differentials across the orifices.
It is still a further object of the applicant's invention to provide a flow divider or combining device which includes a variable orifice structure having a poppet, relief valve mounted for shiftable movement within the opening of the orifice.
It is still a further object of the applicant's invention to provide a flow divider or combining structure which includes a variable orifice structure having a poppet, relief valve mounted for shiftable movement within the opening of the orifice and which allows, through a selected shaping of the poppet, relief valve, a programmable relationship between the differential pressures occurring through the circuit and the flow volumes thereof.
These and other advantages of the applicant's invention will more fully appear from a consideration of the accompanying description which incorporates the included drawings.